How to Manage Pests
UC Pest Management Guidelines
Scientific name: Choristoneura rosaceana
(Reviewed 8/06, updated 3/09, pesticides updated 10/15, corrected 10/16)
In this Guideline:
DESCRIPTION OF THE PEST
Obliquebanded leafroller overwinter as third instar larvae under bud scales. Larvae are yellowish green with brown to black heads. As they mature, larvae construct tubular shelters from a single leaf. There are two generations a year. Periodically, localized infestations of obliquebanded leafroller occur and the larvae of the summer generation can cause serious damage in July and August. Obliquebanded leafroller is rarely a pest in Central Coast orchards.
Larvae feed on flower parts and on fruit early in the season, causing deep depressions that eventually become rough and russeted by harvest. Damage from the summer generation is usually more serious and results in superficial skin tunnels or small holes near the stem portion of the fruit.
Obliquebanded leafroller can occur in orchards in spring and summer. Summer damage is most commonly seen in orchards where a switch is made to the use of highly selective materials (including mating disruption) against codling moth that do not control obliquebanded leafrollers.
The parasitic wasp Macrocentrus iridescens has been observed attacking obliquebanded leafroller larvae in the Central Valley and in Central Coast and North Coast apple orchards.
Organically Acceptable Methods
Sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are organically acceptable.
Monitoring and Treatment Decisions
The best time to treat obliquebanded leafrollers is in spring, around pink bud, before the larvae are sheltered under leaves and between fruit clusters. Apply materials before bees are placed in orchards or after they are removed. Control overwintering larvae with either a delayed dormant application of oil and insecticide or a bloom application. If orchards have experienced damage from this pest in previous years or if leafrollers were observed in spring, also monitor the summer generation. Take fruit and leaf cluster samples at pink bud and in July and August. Tentative thresholds are two or more live larvae in a 100 fruit cluster sample in spring, and four or more in summer.
UC IPM Pest Management Guidelines:
Insects and Mites
L. R. Wunderlich, UC Cooperative Extension, El Dorado County
Acknowledgment for contributions to Insects and Mites:H. L. Andris, UC Cooperative Extension, Fresno County
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
W. W. Coates, UC Cooperative Extension, San Benito County
C. Pickel, UC IPM Program, Sutter/Yuba counties